1. Field of the Invention
The present invention relates to a cantilever of a scanning probe microscope.
2. Description of the Background Art
A scanning probe microscope (SPM) can analyze and estimate a surface of a sample in an nm scale.
The SPM is roughly divided into two portions. One of the SPMs is a scanning tunneling microscope (STM) for operating the inside of a two-dimensional plane while measuring a tunnel current flowing between a surface of a sample having a conductivity and a stylus of a metal (which will be hereinafter referred to as a xe2x80x9cprobexe2x80x9d), thereby three-dimensionally displaying information about the surface of the sample. The other SPM is an atomic force microscope (AFM) for measuring interatomic force acting between a tip of a probe and a surface of a sample from a displacement of a very small leaf spring (hereinafter referred to as a xe2x80x9ccantileverxe2x80x9d) and operating the inside of a two-dimensional plane, thereby three-dimensionally displaying information about concavo-convex portions formed on the surface of the sample.
The AFM is different from the STM in that it can also estimate an insulating material and does not place restrictions on a sample in principle. A measuring method and an operation principle will be described below by taking the AFM as an example.
FIG. 10 is a diagram illustrating a device structure of the AFM. As shown in FIG. 10, a probe 2 is fabricated in the vicinity of a tip of a cantilever 1 and a tip of the probe 2 is provided close to a surface of a sample 4. The sample 4 is mounted on a stage 5.
A laser beam 3 is irradiated on a rear face of the cantilever 1 and reflected light thereof is received by a photodiode 6, and an amount of detection obtained by the photodiode 6 (an amount of warpage of the cantilever 1) is given to a feedback loop section 7. The feedback loop section 7 sends a control signal (a signal indicative of an amount of change in a vertical direction of a piezo 8) to the piezo 8 based on the amount of detection such that the amount of detection is always constant. Upon receipt of the control signal of the feedback loop section 7, the piezo 8 brings the cantilever 1 up and down in the vertical direction based on the control signal. Moreover, the piezo 8 includes a piezo for moving the cantilever 1 in X and Y directions as well as the vertical direction.
With such a structure, the AFM first moves the sample 4 such that the probe 2 fabricated in the tip of the cantilever 1 comes to a portion just above a measuring point. Next, when the cantilever 1 is brought down and the probe 2 is caused to approach the surface of the sample 4, interatomic force is generated between the surface of the sample 4 and the probe 2. Basically, the amount of change in the interatomic force on each measuring point in the sample 4 is measured by the laser beam 3, the photodiode 6 and the feedback loop section 7, thereby detecting concavo-convex portions formed on the surface of the sample 4.
The AFM has three kinds of measuring modes, for example, a contact mode, a tapping mode and a non-contact mode.
In the contact mode, the probe 2 is caused to come in contact with the surface of the sample 4 and the concavo-convex portions formed on the surface of the sample 4 are measured from a displacement of the cantilever 1 (the amount of warpage of the cantilever 1).
In the tapping mode, the cantilever 1 is oscillated to cause the probe 2 to periodically come in contact with the surface of the sample 4, thereby measuring the concavo-convex portions formed on the surface of the sample 4 with a change in an oscillation amplitude which is caused by a variation in the interatomic force generated between the cantilever 1 and the surface of the sample 4.
In the non-contact mode, the probe 2 is not caused to come in contact with the surface of the sample 4 and the concavo-convex portions formed on the surface of the sample 4 are measured with the change in the oscillation amplitude which is caused by the variation in the interatomic force generated on the cantilever 1 and the surface of the sample 4.
The photodiode 6 detects the displacement of the cantilever 1 and the change in the oscillation amplitude as a change in an angle of the laser beam 3 reflected by the rear face of the cantilever 1. The feedback loop section 7 gives a control signal to the piezo 8 to carry out feedback control such that the amount of warpage of the cantilever 1 is always constant in the contact mode and the oscillation amplitude of the cantilever 1 is maintained to be constant in the tapping and non-contact modes.
An amount of movement in a vertical direction on each measuring point in the sample 4 (the control signal of the feedback loop section 7) can be stored in an external computer and the computer can three-dimensionally display the concavo-convex portions formed on the surface of the sample 4 based on the stored data.
Moreover, the AFM can measure the concavo-convex portions formed on the surface of the sample 4, and furthermore, can measure various electrical characteristics of the sample 4, for example, the resistance, magnetic force and surface potential of the sample 4 and the like simultaneously with the measurement of the concavo-convex portions. In this case, it is necessary to change the cantilever 1 and the measuring mode corresponding to a measuring item.
An operation will be described by taking a measurement of a current of the sample 4 as an example. FIG. 11 is a diagram illustrating the device structure of the AFM in the case in which the current of the sample is to be measured.
FIG. 11 is a diagram illustrating the device structure of the AFM in which a resistance can also be measured. As compared with FIG. 10, the cantilever 1 is replaced with a conductive cantilever 1C and the probe 2 is replaced with a conductive probe 2C. A signal cable 9 is provided for sending an electrical characteristic signal of a sample such as a current measured by the conductive probe 2C to a signal processor 10. The signal processor 10 performs a signal processing such as signal amplification for the electrical characteristic signal of the sample measured by the conductive probe 2C. There is provided a DC voltage 11 to be applied to the sample for measuring a resistance.
As shown in FIG. 11, a substance formed of a conductive material is used for the conductive cantilever 1C and, for example, a substance obtained by implanting an impurity into Si (silicon), a substance formed by depositing a conductive film over a Si cantilever or the like is used. The conductive cantilever 1C and the conductive probe 2C are used in place of the probe when the electrical characteristic is to be measured by a tester. In order to measure the current of the sample 4, it is necessary to cause the conductive probe 2C to come in contact with the surface of the sample 4. The measurement is carried out in the contact mode.
A voltage is applied between the sample 4 and the probe (conductive probe 2C) while measuring the concavo-convex portions formed on the surface of the sample 4 by the measuring method in the contact mode, and a current flowing between the sample, the probe and the cantilever is measured as the electrical characteristic signal. The electrical characteristic signal obtained by the conductive probe 2C is sent from the conductive cantilever 1C to the signal processor 10 through the signal cable 9 and data subjected to a signal processing based on the electrical characteristic signal by the signal processor 10 are stored in a computer, and the computer can three-dimensionally display measurement data such as a resistance value of the sample which is calculated based on the stored data.
In the case in which the electrical characteristic of the sample other than the concavo-convex portions formed on the surface of the sample, for example, the resistance, the surface potential and the like are to be measured by the conventional atomic force microscope (AFM), the electrical characteristic signal measured by the probe is sent from a cantilever to a signal processing circuit such as an amplifier through a signal cable. Therefore, a noise is mixed into the electrical characteristic signal during transmission from the probe or a signal level of the electrical characteristic signal is reduced. For this reason, there is a problem in that the resolution or precision of measurement data is reduced to cause a reduction in precision in a measurement.
A first aspect of the present invention is directed to a scanning probe microscope having a probe for sample analysis and acquiring measurement data based on an electrical characteristic signal of a sample obtained from the probe, wherein the probe has a pyramid structure, and a signal processing section for performing a signal processing of the electrical characteristic signal to suppress a deterioration in the electrical characteristic signal is provided on/in a side surface of the probe.
A second aspect of the present invention is directed to the scanning probe microscope according to the first aspect of the present invention, wherein the signal processing section includes a semiconductor integrated circuit fabricated in a side surface of the probe.
A third aspect of the present invention is directed to the scanning probe microscope according to the first aspect of the present invention, wherein the signal processing section includes a semiconductor device adhered to a side surface of the probe.
A fourth aspect of the present invention is directed to the scanning probe microscope according to any of the first to third aspects of the present invention, wherein the signal processing section includes an amplifying circuit for amplifying the electrical characteristic signal.
A fifth aspect of the present invention is directed to the scanning probe microscope according to any of the first to third aspects of the present invention, wherein the signal processing section includes a memory for storing the electrical characteristic signal.
A sixth aspect of the present invention is directed to the scanning probe microscope according to the fifth aspect of the present invention, wherein the memory includes a DRAM.
A seventh aspect of the present invention is directed to the scanning probe microscope according to the fifth aspect of the present invention, wherein the memory includes an SRAM.
An eighth aspect of the present invention is directed to the scanning probe microscope according to the fifth aspect of the present invention, wherein the memory includes a flash memory.
A ninth aspect of the present invention is directed to the scanning probe microscope according to any of the first to third aspects of the present invention, wherein the signal processing section includes a microprocessor for performing a predetermined operation processing for the electrical characteristic signal.
A tenth aspect of the present invention is directed to the scanning probe microscope according to any of the first to seventh aspects of the present invention, wherein the signal processing section includes a plurality of signal processing sections for performing signal processings which are different from each other, the plurality of signal processing sections are provided on/in different side surfaces of the probe, respectively, and are isolated from each other.
According to the first aspect of the present invention, the signal processing of the electrical characteristic signal is performed by the signal processing section provided on/in the side surface of the probe. Therefore, it is possible to perform the signal processing, for example, to avoid a disturbance such as a noise generated when propagating the electrical characteristic signal from the probe. Thus, it is possible to effectively suppress a reduction in precision in a measurement.
According to the second aspect of the present invention, the semiconductor integrated circuit is fabricated in the side surface of the probe. Consequently, it is possible to obtain a signal processing section having a high stability which is firmly integrated with the probe.
According to the third aspect of the present invention, the semiconductor device is adhered to the side surface of the probe. Consequently, the semiconductor device can be adhered to the side surface of the probe after it is manufactured independent of the probe. Correspondingly, it is possible to relieve time and labor required for the manufacture.
According to the fourth aspect of the present invention, the amplifying circuit is provided on/in the side surface of the probe. Consequently, it is possible to obtain an amplified electrical characteristic signal which is resistant to a disturbance such as a noise.
According to the fifth aspect of the present invention, the memory is provided on/in the side surface of the probe. Consequently, the electrical characteristic signal obtained by the probe can be stored in such a situation that there is no room for mixing a disturbance such as a noise. Accordingly, it is possible to obtain measurement data having high precision based on the electrical characteristic signal stored in the memory.
According to the sixth aspect of the present invention, the DRAM is provided on/in the side surface of the probe. Consequently, it is possible to store an electrical characteristic signal having a large capacity.
According to the seventh aspect of the present invention, the SRAM is provided on/in the side surface of the probe. Consequently, it is possible to store an electrical characteristic signal with comparatively low power consumption.
According to the eighth aspect of the present invention, the flash memory is provided on/in the side surface of the probe. Consequently, it is possible to store an electrical characteristic signal with a high stability irrespective of the presence of power supply.
According to the ninth aspect of the present invention, the microprocessor is provided on/in the side surface of the probe. Consequently, it is possible to substitute a predetermined operation processing for a part of a measurement data operation processing based on the electrical characteristic signal.
According to the tenth aspect of the present invention, it is possible to perform a comparatively complicated processing by linking the respective signal processings of the signal processing sections together.
In order to solve the above-mentioned problem, it is an object of the present invention to provide a scanning probe microscope capable of effectively suppressing a reduction in precision in a measurement.